Her is a little bit of information on the dirt cars racing in Oklahoma.....
Most everyone is getting the chain and rear sprockets from Daves Discount Motors.
The chain is #25 pitch but most importantly, it needs to be "HD" (heavy duty).....the HD chain has thicker plates that are more stable on the pins and this is all that Daves sells (8.00$ per foot).
The standard #25 chain (even the high dollar stuff) will start to bind up real bad as the plates seam to "pull together" and start causing interference and binding up. Doesnt matter how clean and oiled you keep it, the plates just work towards each other when in tension. You can spread them out and free it up and in one run, it will be bound up again.
Rear sprockets are for "go peds" and have a 4 bolt pattern that doesnt really match up to anything currently available (that I know of) so most of us make a sprocket hub ourselves.
The rear sprockets are available in different sizes (56, 60, 64, ect) and alot of us run a 10/64 (6.4 final drive ratio) BUT we also run tall dirt tires. The 64 tooth sprocket is pretty big and wont work with a small left rear tire.
The front sprocket is where there are several options....you can find all kinds of #25 pitch sprockets for pocket bikes, scooters as well as equipment like printing presses and ect. The pocket bike and scooter stuff is available from Daves in about 5 teeth to about 10 teath and they mostly screw on with a metric thread and alot of them are pre-hardened. They are made on a threaded post so you can just modify the clutch bell shaft to accept the threaded sprocket pretty easily.
The equipment sprockes are mounted to a hub with a .250" hole and can be bolted on that way or reamed to slide onto the shaft. They are also made from soft material and need to be hardened to last and are available in about 9 teeth and bigger.
Then there is a chain guide system required. Alot of guys have gone to nylon plates mounted on each side of the rear sprocket to keep the chain on the rear sprocket and then some make a chain tensioner with rollers to trap the chain and guide it onto the sprocket....either way, you have to have something to keep the chain from falling off.
Hope this helps a little. I am sure someone could post pics if you needed to see it.
got the chain drive almost done thanks Harper for the info. Looks like the 64 will only work with the dirt pin tires so I am going to get some other gears in case I want to change tires but looks real good just have to work on the chain guard issue now.